X-ray imaging system

Abstract

A method of performing scatter correction on an X-ray image is disclosed. The method comprises obtaining an input image for processing based on a source X-ray image of a sample acquired using an X-ray detector, and determining a model of the sample based on the input image. The model is then evaluated by computing, based on the model, simulated X-ray image data and evaluating the simulated image data against the input image to determine whether a convergence criterion is fulfilled. An updated model of the sample is generated if the convergence criterion is not fulfilled. The model evaluating step is repeated based on one or more successive updated models until the convergence criterion is fulfilled in a final iteration, and scatter correction is then performed on the source X-ray image using simulated image data computed during the final iteration.

1 . A method of configuring an X-ray image processing system comprising an X-ray imaging system and a simulator for generating simulated X-ray image data, the method comprising:
 generating simulated X-ray images for a plurality of samples, wherein for each sample, simulated X-ray image data is generated for each of a plurality of distinct configurations of the X-ray imaging system;   accessing real X-ray images for each of the plurality of samples acquired using the X-ray imaging system;   for each of the configurations, fitting a transfer function between the real X-ray images and the simulated X-ray images, the transfer function defining a translation between real and simulated image data;   determining a similarity metric between simulated and real images based on the transfer function for each configuration;   
       selecting a given configuration and the associated transfer function based on the similarity metrics; and 
       configuring the X-ray image processing system based on the selected configuration and transfer function. 
     
     
         2 . A method according to  claim 1 , wherein the plurality of configurations comprise one of:
 a plurality of distinct X-ray output settings, optionally specified as emitter voltages;   a plurality of distinct filtration settings, optionally specified as thicknesses of a filtration material used in the imaging system; and   a plurality of distinct combinations of output and filtration settings.   
     
     
         3 . A method according to  claim 1 , wherein the samples comprise samples of at least two material types, optionally comprising polymethyl methacrylate and aluminium. 
     
     
         4 . A method according to  claim 3 , wherein the samples comprise material samples of a plurality of distinct thicknesses for each of the at least two material types. 
     
     
         5 . A method according to  claim 3 , wherein generating simulated X-ray images comprises, for each sample:
 accessing a calibration training database, comprising scatter kernels for each of the materials across a predetermined set of X-ray output and filtration values, optionally covering a predetermined range of output and filtration values in predetermined step sizes; and   for each output and filtration value, creating a simulated image using the scatter kernels for the given output and filtration values for the given material of the sample.   
     
     
         6 . A method according to  claim 1 , wherein the transfer function comprises a mathematical function, preferably based on a second or higher degree polynomial. 
     
     
         7 . A method according to  claim 1 , wherein the transfer function defines a translation function which varies across the image. 
     
     
         8 . A method according to  claim 7 , wherein the transfer function defines a respective translation for each pixel of the image, optionally as a distinct polynomial function or other function at each pixel location. 
     
     
         9 . A method according to  claim 1 , wherein the real and simulated X-ray images comprise intensity values specified at each of a plurality of pixel locations, and wherein fitting the transfer function comprises fitting the transfer function based on logarithms of the intensity values. 
     
     
         10 . A method according to  claim 1 , wherein configuring the image processing system comprises configuring the simulator to generate simulated image data based on the selected configuration, optionally comprising a given output and filtration setting. 
     
     
         11 . A method according to  claim 1 , wherein configuring the image processing system comprises configuring the image processing system to use the transfer function to evaluate simulated images against real X-ray images. 
     
     
         12 . A method according to  claim 11 , wherein configuring the image processing system comprises configuring the image processing system to use the transfer function to evaluate simulated images against real X-ray images by applying the transfer function to simulated or real image data to translate image data between real and simulated image domains and/or to enable comparison of real and simulated image data. 
     
     
         13 . A method according to  claim 1 , wherein the simulator implements a Monte Carlo model, and wherein the configuration is performed to match the behaviour of the Monte Carlo model to the observed real-world behaviour. 
     
     
         14 . A method according to  claim 1 , wherein the transfer function is material-invariant. 
     
     
         15 . A method according to  claim 1 , comprising using the transfer function in a process for generating composition information for a sample based on an X-ray image and/or performing scatter correction on an X-ray image. 
     
     
         16 . A method according to  claim 1 , comprising:
 obtaining an input image for processing based on a source X-ray image of the sample acquired using an X-ray detector;   
       determining a model of the sample based on the input image;
 evaluating the model by a process comprising: 
 
       computing, based on the model, simulated X-ray image data using a simulator configured based on the selected configuration;
 evaluating the simulated image data against the input image using the selected transfer function to determine whether a convergence criterion is fulfilled; and 
 generating an updated model of the sample if the convergence criterion is not fulfilled, the updated model generated using the simulated image data, optionally using a scatter-corrected version of the input image generated using the simulated image data; 
 repeating the model evaluating process based on one or more successive updated models until the convergence criterion is fulfilled in a final iteration; 
 the method further comprising at least one of:
 outputting composition information for the sample, optionally thickness and/or material composition data for respective regions or pixels of the input image, optionally based on the model of the sample used to generate the simulated image data determined to meet the convergence criterion during the final iteration; and 
 performing scatter correction on the source X-ray image using simulated image data computed during the final iteration. 
 
 
     
     
         17 . A system having means, optionally in the form of a processor with associated memory, for performing the method of  claim 1 . 
     
     
         18 . A computer-readable medium comprising software code which when executed is arranged to perform the method of  claim 1 .